Aviation gasoline production



H84 TING t E. B. PECK AVIATION GASOLINE PRODUCTION Filed larch 11, 1942 Pnmrrngc Con yams:

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Patented Oct. 15, 1946 AVIATION GASOLINE PRODUCTION Edward B. Peck, Elizabeth, N. J assignor, by

mesne assignments, to Standard Catalytic Company, a corporation of Delaware Application March 11, 1942, Serial No. 434,206

'ularly, it relates to improvements in the production of aviation gasoline by removing from gasoline or naphthas low octane fractions by fractional distillation and thereafter subjecting the low octane fractions removed to a two-stage operation, in the first stage of which naphthenes present in the said low octane fraction are dehydrogenated to form the-' corresponding aromatic derivatives, thence separated from the parafiins, and in the second stage of which the paraffinic constituents are aromatized catalytically.

Prior to my invention, it was known that the octane number of a gasoline could be improved by removing certain fractions by distillation, and it has been further proposed to hydroform the low octane number fractions and blend them back into the gasoline. For example, it has been proposed heretofore, in order to improve the octane rating of the gasoline and particularly the octane rating as determined by actual road tests, to separate the intermediate fractions, say those boiling within the range of from ZOO-325 F., and to subject these fractions to a catalytic reform ing operation in th presence of added hydrogen and thereafter to combine the hydroformed fraction with the other fractions to produce a gasoline of greatly improved octane rating.

The present invention as stated. carries out the conversion of the low octane fraction of a proper operating conditions, and I prefer to use a catalyst composed of a mixed sulphide of nickel and tungsten (2 mols of NiS and 1 mol of W83).

After separation of the aromatics and hydrogenated olefins by distillation and/or solvent extractions, the normal paraffinic residue is aromatized. The aromatized can be carried out using chromic oxide catalyst supported on activated alumina or some other suitable catalyst.

, The main object of my present invention therefore is to distill a gasoline or naphtha of low octane number to separate out the lowest octane fractions, to leave a residue of greatly improved octane rating, and to subject the separat- 1 Claim. (01. 196-49) ed fraction to a two-stage catalytic treatment to produce aromatics.

A more specific object of my present invention is to separate from a gasoline or naphtha of low octane number the lowest octane fraction and to produce from the separated fraction by a combination of dehydrogenation and aromatization, toluene under conditions conducive to maximum yields and minimum coke formation.

A still more specific object of my invention is to segregate at least one of the low octane fractions of a naphtha, to thereafter subject the fraction to catalytic reforming in the presence of hydrogen to aromatize the naphthenes and reduce unsaturation by hydrogenating olefinic hydrocarbons, to thereafter separate the naphthene conversion products from th unchanged parafiinic constituents, and then to aromatize the said parafiin constituents.

A still further object of my invention isto subject a fraction of the naphtha or gasoline boiling within the range of from about 180-220 and containing naphthenes and heptane parafnns and olefins essentially to a two-stage process, in the first stage of which the naphthenes are converted to aromatics, while the heptanes are substantially unchanged, and after separation of the aromatics from the parafiins to convert the latter to toluene.

Other and further objects of my invention will appear from the following more detailed description and claim.

My invention will be best understood by setting forth a specific example illustrating a preferred modification of my invention and also by reference to the accompanying drawing in which I have set forth diagrammatically a fiow plan illustrating apparatus elements in which my improved process may be carried into practical effect.

Referring in detail to the drawing, an East Texas virgin gasoline boiling within the range of from about YO-300 F. and having an octane number as determined by the A. S. T; M. method of 60, is charged to the system through line I,

thence heated in a furnace 3 tovaporization temperatures, thence withdrawn through line 4 and discharged into a fractionating column 6. An overhead fraction and a bottoms fraction are recovered through lines 8 and Hi, respectively, and these fractions are combined and collected in a receiving drum l2. This product in the example given will have an octane number of about 70. An intermediate fraction boiling from ISO-220 F. is withdrawn from the fiactionator through line M. This fraction withdrawn from the system through line I4 contains naphthenes and. normal heptane, together with some olefin's, although the amount of the latter is rather limited.

This material is discharged into a second furnace 16 where it is heated to a temperature of about 800-950" F..and thence discharged through line [8 into a reaction vessel 20 containing catalyst, which catalyst is nickel tungsten sulfide. In order to saturate any olefins present in the hydrocarbons charged to reaction vessel 20, hydrogen from some source is also discharged into the reactor 20 through lines'22 and .18, the amount of hydrogen being such that it exerts a partial pressure of 50-80% of the total pressure. The pressure prevailing within reactor '20 is of the order of 750-1000 lbs/sq. in., and the feed rate is of the order of about 0.5 volume of oil per volume of reactor per hour. Under the conditions stated, the naphthenes are dehydrogenated to form toluene, while the parafiins present .in the' y'apors are substantially unchanged. Reaction products are withdrawn overhead from re- =a'ctor"2ll through line 26 and discharged into a second fractionator 28. From fractionator 28, the toluene formed is Withdrawn through line 30. The overhead product consisting essentially of heptane is withdrawnthrough line 32, thence discharged into a third heater 34 where it is heated to a=temperatureoffrom about 900-1050 with a temperature-of about 960 F. being preferred, and at this temperature the heptane is with- "drawn through line-36 and-discharged into a secondreactor fill-containing a catalyst such as chromium oxide supported on activated alumina, the portions being approximately 9 parts by weight of alumina per 1 part of chromium oxide. Instead of using chromium'oxide, molybdenum oxide maybe used.

The pressure prevailing in reactor 49 is about 1 atmosphere gauge pressure, and the material is fed to the reactor at a rate of about 0.5 volume of oil per volume of reactor per hour on a cold oil basis. The reaction products containing toluene are Withdrawn through line 42 and discharged into a fractionator 44 from which toluenemay be recovered through line 46. The over head fraction is Withdrawn through line 68 and recycled to line 32 for further treatment in reactor '40. The toluene collected through lines 30 and 46 is discharged into equipment (not shown) to refine and purify the same and to produce a product of any desired degree of purity. The "actual purification of this product is well known to the priorart and need not be described in detail-herein.

It will '-be appreciated that in both reactors 20 and-'40, it will be necessary periodically to discontinue the operation to regenerate the catalyst in said reactors since, due to the reaction, carbonaceous deposits are formed on the said catalyst. The method of regenerating the catalyst most commonly employed is that wherein it is treated with an oxygen containing gas under such conditions of temperature and pressure as to burn the carbonaceous deposits formed there on. This regeneration .method'isalso well known to the art. It should be pointed out that instead of using :stationary beds of :catalyst inreactors '20 and 40, a powdered catalyst may be :used and the catalyst may be suspended in the reaction vapors by means already known, during the reaction period and thereafter separating catalyst from the reaction products and returnvIn other.

tact between catalyst and reactants under reaction conditions may be used in my improved process.

It will be understood that numerous modifications of my invention may be made by those :skilled in the art without departing from the spirit thereof. The fracticn separated through line H, for example, from fractionator 6 may have a different boiling range from that hereinbefore set forth, namely, from 180-220 F., that is to say, it may be a hexane or an octane fraction and, if so, of course the aromatic product produced would be benzene or one of the xylenes. Alsoythe original charging stock may have a different boiling range from that hereinbefore set forth, although preferably it is a fraction boiling within the gasoline range. Furthermore, also it should be pointed out that the charging oil delivered .to the system through .line I may be a cracked stock, that-is to say, it may be a gasoline fraction produced by thermally or catalytically .cracking gas oil and, if so, it may contain considerable quantitiesoi olefins which means that the amount of hydrogen employed in reactor .20 should be sumcient to saturate the olefins. If it :is acracked gasoline, particularly if it :is .a catalytically cracked gasoline, the removal of the lowest octane fractions may produce a residual product of very high octane rating, namely, an aviation gasoline or a base stock which may be blended with relatively small quantities, say 15-20% by volume, of alklated isobutane or other .alkylates, to produce a high quality 'avia- :tion gasoline. Also, itshould be pointed out that in the dehydrogenation of naphthenes carried out .in reactor 20, I may use mixtures of sulfides of the III and V group elements of the periodic system.

It should be noted that one of the major advantages of my present invention resides in the feature that less coke is produced in my two-stage process, since I treat the materials under conditions which are less conducive to coke formation. i. -.e., by treating naphthenes and parafiins sepa- .rately.

.It is .my intention to claim all of the subject matter inherent in my invention, except that excluded by the terms of the appended claim.

What I claim is:

The method of treating a hydrocarbon oil cracked stock containing olefins, naphthenes and paraffins and boiling substantially within the gasoline range, to produce separately aromatic compounds and a gasoline of substantially higher knock .rating than said cracked stock, which comprises vaporizing said cracked stock, passing the vapors through a fractionating zone, removing a light fraction, an intermediate hexane to octane fraction, and .a heavy fraction, said light fraction and said heavy fraction containing compounds having relatively high anti-knock value as compared with said intermediate fraction, 0 combining said light fraction and said heavy fraction to form gasoline, passing said intermediate fraction through a heating coil and thence into a hydrogenation zone in which naphthenes 'are converted into aromatic compounds and olefins are saturated, thereby forming a product consisting principally of aromatic compounds and 'paraffins of 6 to 8 carbon atoms "per molecule, separating the aromatic compounds and the 6 to 8 carbon atom paraffins, passing the 6 to 8 car- 0 bon atom parafiins through a heating coil and thence into a zone where they are converted into a product composed mainly of aromatics, and combining the aromatics produced by the two conversion stages 'hereinbefore recited.

- EDWARD B.'PECK. 

